1. Field of the Invention
The present invention relates to a video watermarking apparatus and method. More particularly, the present invention relates to an apparatus and method of watermarking a video in a compression domain, substantially resisting a digital video interactive (DVI) capture attack of the video.
2. Description of Related Art
Generally, due to the pervasiveness of digital media and various multimedia data transmission and storage devices, and the development of authoring tools, multimedia data may be easily copied and distributed via a network. Therefore, new services are provided, but problems relating to the adequate protection of the copyright of the digital media have seriously increased.
Watermarking is a method provided for protecting the copyright of the digital media and comprises the steps of inserting a watermark that is a signature of an author or information identifying the author into the digital media. In doing so, the method solves the problem of protecting the copyright by inserting the watermark into the digital media, and when a problem of proving copyright infringement occurs, allows for extracting the watermark to show proof of copyright ownership.
Methods of watermarking may be largely classified into methods of watermarking in a spatial domain, and methods of watermarking in a compression domain.
Since various algorithms may be applied to conventional methods of watermarking in the spatial domain, benefits include substantially resisting various attacks.
However, since most video is stored and transmitted in a compressed form, to apply a method of watermarking in the spatial domain, an entire compressed video has to be uncompressed and the uncompressed video has to be compressed again after inserting a watermark into the uncompressed video. Therefore, there are problems relating to inserting the watermark and compressing the uncompressed video again, and there are an undesirably large amount of required computations that are related to the process of uncompressing the entire compressed video.
A method of reducing the large amount of computations, which is a disadvantage of the conventional method of watermarking in the spatial domain, includes a method of watermarking in the compression domain, operating in a bit stream of the compression domain. However, in such conventional methods of watermarking in the compression domain, since a watermark is directly inserted into/extracted from a compressed discrete cosine transform (DCT) coefficient, the methods can be relatively ineffective against a recompression attack of a video.
Hartung, Cox, and Langelaar methods are representative examples of conventional methods of watermarking in a compression domain. The Hartung method for example, as disclosed in U.S. Pat. No. 5,809,139, the entire disclosure of which is incorporated herein by reference, has a disadvantage of requiring a large amount of computations because a very complex circuit is required for preventing error propagation and an increase of bit rates, due to a watermark in a compression domain.
In the Cox method for example, as disclosed in U.S. Pat. No. 5,915,027, the entire disclosure of which is incorporated herein by reference, since an inserted watermark affects only frequency features of data in a compression domain, a simple and effective attack against the watermark can occur when there is a change in bit rates and frame structures while recompression of a video and additional computation caused by shaping of the watermark is required.
In the Langelaar method, a very quick computation is possible in a compression domain but there is a disadvantage of having a structure that is very weak in recompression of a video.
Accordingly, a need exists for a system and method for effectively and efficiently watermarking a video in a compression domain.